These opcodes will always call out to a C function for now.

R=titzer@chromium.org

Bug: v8:6600
Change-Id: I0ba8984d593c0203b46c2814dec4c091754df99a
Reviewed-on: https://chromium-review.googlesource.com/860924
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50551}